DE 30 07 361 C3 of the species has already disclosed such a mass flow meter. The mass flow meter, which in this case has a symmetrical design, can consist of an influx flange and an efflux flange which form the connection between influx and efflux tube branches and external influx and efflux tubes. A measurement tube connects the influx and efflux tube branches so as to provide the mass flow meter with a shape like the Greek letter Ω.
Embodiments with double parallel tube layouts are also widely known in the prior art. An influx acquisition point and an efflux acquisition point respectively lie at the connection sites. Each mass flow meter of the type in question here is based on the following physical principle:
An excitation unit sets the measurement tube in oscillation. The oscillations recorded at the influx and efflux acquisition points show the same phase. When flow takes place through the mass flow meter, the fluid mass experiences accelerated oscillation excursions, which generate a Coriolis force. The originally uniform oscillation of the tube then experiences effects due to the Coriolis force distributed along the measurement tube, which causes a phase shift at the influx and efflux acquisition points. The oscillation phases and oscillation amplitudes at the influx and efflux acquisition points are recorded by means of influx and efflux oscillation sensors, and are delivered to an electronic evaluation unit. The size of the phase shift is a measure of the mass flow.
By calibration, the way in which the phase shift correlates with the mass flow is established for each such Coriolis mass flow meter. These parameters are used for signal processing by the electronic evaluation unit. The signal processing of the measurement signal obtained by the oscillation sensor is made more difficult by the fact that considerable noise effects are superimposed on the usually very small measurement effect. The underlying noise signals may be many times greater than the useful signal component determined by the Coriolis effect.